1. Technical Field
The present invention relates to semiconductor characterization in general, and in particular to a method and apparatus for measuring the dopant profile of a semiconductor. Still more particularly, the present invention relates to a method and apparatus for measuring a two-dimensional dopant profile of a semiconductor.
2. Description of the Prior Art
Present-day integrated circuit manufacturing technology demands accurate knowledge of the concentration of dopants that have been incorporated into substrates. This is because dopant concentration within a substrate has a significant effect on the performance of discrete devices, such as transistors, that are built on the substrate. In addition, it is also important to have the knowledge of the dopant concentration in a spatial extent for process development.
Typically, the active region of a field-effect transistor (FET) is engineered by incorporating dopants, such as arsenic, boron, or phosphorate, in a concentration ranging from 1015 cm−3 to 1020 cm−3. When building FETs at a submicron level, it is necessary to quantify the variation of the above-mentioned dopants at the junction regions of submicron FETs to a resolution of 10 nm or less over four orders of magnitude in dopant concentration.
There are several prior art techniques for measuring dopant profiles of a semiconductor, which include Scanning Capacitance Microcopy, Scanning Kelvin Probe Microscopy, Scanning Preading Resistance Microscopy, etc. However, all of the prior art techniques generally do not have a very high sensitivity and/or spatial resolution to meet the demands of integrated circuit manufacturing at submicron levels. Furthermore, the sensitivity of some of the prior art techniques tends to decrease as the spatial resolution increases with the usage of sharper probes. Consequently, it would be desirable to provide an improved method and apparatus for measuring dopant profile of a semiconductor.